BACKGROUND
1. Technical Field
The present disclosure relates to a wireless communication device employing an antenna.
2. Description of Related Art
A dual-band antenna is commonly a planar antenna, which includes a first radiating portion for transmitting/receiving wireless signals at high frequencies and a second radiating portion for transmitting/receiving wireless signals at low frequencies The first and second radiating portions are usually connected to a feed end of the dual-band antenna. During testing of specific absorption rate (SAR) of the dual-band antenna, current from the feed end may be added together. Since the SAR mainly depends on the current intensity of the antenna, thus SAR at the feed end becomes too high, which may negatively influence users.
Therefore, there is room for improvement within the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views.
The FIGURE is an isometric view of a wireless communication device, according to an exemplary embodiment.
DETAILED DESCRIPTION
The disclosure is illustrated by way of example and not by way of limitation in the FIGURES of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.”
The FIGURE shows a
wireless communication device 100 according to an exemplary embodiment. The
wireless communication device 100 may be a mobile phone or a personal digital assistant, for example.
The
wireless communication device 100 includes a
base board 10, an
antenna 20, a
metal assembly 30, and a
conductive assembly 40. The
antenna 20 is located above the
base board 10, the
metal assembly 30 and the
conductive assembly 40 are positioned at a side of the
base board 10.
The
base board 10 is a printed circuit board (PCB) of the
wireless communication device 100, and is made of composite materials. A
feed portion 11 and a
ground portion 12 are electrically mounted on the
base board 10. The
feed portion 11 provides current to the
antenna 20, and the
antenna 20 is grounded by the
ground portion 12. In one exemplary embodiment, the
feed portion 11 is a circular shaped metal sheet, current on a center of the
feed portion 11 is greater than current on other positions of the
feed portion 11.
A keep-out-zone S is defined at a side of the
base board 10. The purpose of keep-out-zone S is to not permit other elements (such as a camera, a vibrator, a speaker, etc.) on the
base board 10 to be placed in a predetermined area where it may interfere with the antenna. In one exemplary embodiment, The
antenna 20 is located above the keep-out-zone S, the
metal assembly 30 and the
conductive assembly 40 are positioned at the keep-out-zone S.
In one exemplary embodiment, the
antenna 20 is a planar inverted-F antenna (PIFA), and includes a
feed end 21, a
ground end 22, a
connection body 23, a
first radiator 24, and a
second radiator 25. The
feed end 21 is electronically connected to the center of the
feed portion 11. The
connection body 23 is a rectangular sheet, and is perpendicularly connected to a distal end of the
feed end 21. Both of the
first radiator 24 and the
second radiator 25 are connected to the
connection body 23, and a gap (not shown) is defined between the
first radiator 24 and the
second radiator 25. The
ground end 22 is electronically connected to the
ground portion 12, and the
second radiator 25 is perpendicularly connected to the
ground end 22. In one exemplary embodiment, the
antenna 20 can receive/transmit wireless signals having the central frequency of about 1852 MHz, 1880 MHz, and 1908 MHz.
Since the
feed end 21 is electronically connected to the center of the
feed portion 11, current from the
feed portion 11 is gathered around the
feed end 21. For example, the current from the
feed portion 11 is gathered at the
feed end 21 and the
connection body 23.
The
metal assembly 30 includes a plurality of metal sheets. In one exemplary embodiment, the
metal assembly 30 includes a
first metal sheet 31 and a
second metal sheet 32. The
first metal sheet 31 and the
second metal sheet 32 are located at the keep-out-zone S, and are spaced from the
first radiator 24 and the
second radiator 25.
The
conductive assembly 40 is connected between the
base board 10 and the
metal assembly 30. In one exemplary embodiment, the
conductive assembly 40 includes a first inductor L1, a second inductor L2, and a third inductor L3. The first inductor L1 is connected between a peripheral edge of the
feed portion 11 and the
first metal sheet 31. The second inductor L2 is connected between the
second metal sheet 32 and the
ground portion 12. The third inductor L3 is connected between the
first metal sheet 31 and the
second metal sheet 32.
Referring to the table 1, when the
metal assembly 30 and the
conductive assembly 40 are incorporated into the
wireless communication device 100, the specific absorption rate (SAR) of the
antenna 20 is significantly reduced. For example, when the
antenna 20 receives/transmits wireless signals having the central frequency of about 1852 MHz, the SAR of the
wireless communication device 100 is reduced about 0.19 (1.14−0.95=0.19).
The table 1 sets out a relation among frequencies, SAR of the
wireless communication device 100 having the
metal assembly 30 and the
conductive assembly 40, and SAR of the
wireless communication device 100 lacking the
metal assembly 30 and the conductive assembly
40:
|
|
|
SAR of the wireless |
SAR of the wireless |
|
|
communication device |
100 |
communication device 100 |
|
|
lacking the metal assembly |
having the metal assembly |
|
Frequencies |
|
30 and the conductive |
30 and the conductive |
Signal |
(MHz) |
assembly 40 (1 g) |
assembly 40 (1 g) |
|
WCDMA |
1852 |
1.14 |
0.95 |
BAND 2 |
1880 |
1.42 |
1.06 |
|
1908 |
1.85 |
1.37 |
|
The table 2 shows that when the
metal assembly 30 and the
conductive assembly 40 are incorporated into the
wireless communication device 100, the insertion loss efficiency of the
antenna 20 is significantly reduced, and the radiation efficiency of the
wireless communication device 100 is greater than 20 percent, thereby satisfying communication standards.
Table 2 sets out a relation among frequencies, an insertion loss efficiency of the
antenna 20, and a radiation efficiency of the wireless communication device
100:
|
|
|
|
|
Insertion |
Radiation |
|
|
|
Radiation |
loss |
efficiency of |
|
|
|
efficiency |
efficiency |
the wireless |
|
Frequencies |
Wireless |
of the |
of the |
communication |
Signal |
(MHz) |
communication device |
antenna |
antenna |
device |
|
WCDMA |
1852 |
Lacking the metal |
31.30% |
81.50% |
25.30% |
BAND 2 |
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
|
Having the metal |
28.70% |
75.50% |
21.70% |
|
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
1880 |
Lacking the metal |
31.60% |
87.10% |
27.50% |
|
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
|
Having the metal |
29.10% |
81.00% |
23.60% |
|
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
1908 |
Lacking the metal |
31.70% |
92.60% |
29.00% |
|
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
|
Having the metal |
29.30% |
89.20% |
26.00% |
|
|
assembly 30 and the |
|
|
conductive assembly 40 |
|
Since the
metal assembly 30 is located at the keep-out-zone S, and is electronically connected to the
base board 10 through the
conductive assembly 40, a proportion of the current can be absorbed by the
metal assembly 30, thereby reducing the current intensity on the
feed end 21 of the
antenna 20 and changing distributions of the current on the
antenna 20. Thus, the SAR of the
antenna 20 is significantly reduced. Additionally, the first inductor L1 is connected to the peripheral edge of the
feed portion 11 to obtain small current, thus, the radiation efficiency of the
wireless communication device 100 will not be negatively influenced.
In other exemplary embodiments, the
conductive assembly 40 can be a plurality of capacitors.
In summary, the
conductive assembly 40 obtains a proportion of the current from the
base board 10, and the
metal assembly 30 absorbs the proportion of the current. Thus, the current flowing to the
antenna 20 is reduced, and the
antenna 20 has a dispersed and even electromagnetic radiation field and obtains a reduced SAR.
It is to be understood, however, that even through numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of assembly and function, the disclosure is illustrative only, and changes may be made in detail, especially in the matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.